The present invention relates to vehicles, and, more particularly, to two and three wheeled vehicles which utilize a swing arm upon which the rear wheel is supported.
Two and three wheel vehicles such as motorcycles most usually steer the vehicle by turning only the front wheel(s). In such vehicles, the rear wheel generally is in a fixed position to rotate in a generally vertical plane extending parallel to the longitudinal axis of the vehicle. The rear wheel in motorcycles is frequently supported at the rear end of a swing arm which is pivotably supported at its front end of the chassis or frame of the vehicle.
When such vehicles turn, the front wheel(s) is pivoted about a generally vertical axis in the direction of the turn. However, the rear tire continues its rotation in a vertical plane parallel to the longitudinal axis. The lateral force acting on the tire as the vehicle orients its longitudinal axis in the direction of the turn causes the rear tire to xe2x80x9cscrubxe2x80x9d or slide sideways away from the direction of the turn. Such sidewise movement of the rear tire produces tread wear, the potential for loss of control, and loss of speed.
It is an object of the present invention to provide a novel vehicle rear wheel assembly which enables the rear wheel to pivot about a generally vertical axis to track more closely the turning radius of the front wheel(s).
It is also an object to provide such a vehicle rear wheel steering assembly which is relatively easy and economical to fabricate.
Another object is to provide such a vehicle rear wheel steering assembly in which the rear wheel is hydraulically pivoted together with the front wheel(s).
It has now been found that the foregoing and related objects may be readily attained in a vehicle which has a chassis with a front and rear ends and a longitudinal axis. At least one front wheel is mounted on the front end of the chassis for rotation about a first horizontal axis and for pivoting about a first vertical axis to control the direction of the vehicle. A rigid swing arm has its front end pivotally mounted on the rear end of the chassis for pivoting about a second horizontal axis perpendicular to the longitudinal axis.
On the rear end of the swing is a wheel mounting assembly arm including a hub and pivot means mounting the hub on the rear end of the swing arm for pivotal movement about a second generally vertical axis with respect to the second horizontal axis and the longitudinal axis. Rotatably supported on the hub for rotation about a third horizontal axis is a rear wheel whereby the rear wheel naturally tracks the front wheel in a cooperating turning arc.
Preferably, the vehicle includes a shock absorber having a rear end mounted on the rigid swing arm and a front end mounted on the rear end of the chassis to limit the oscillation or pivotal movement of the rigid arm about the second horizontal axis. A dampening mechanism having a rear end pivotally mounted to the pivot means and a front end pivotally mounted on the swing arm provides tension and resists movement of the hub about the second vertical axis.
The rear wheel assembly includes a clevis member with an axle extending therefrom, bearing means on the axle and a wheel rotatably seated on the bearing means. The wheel mounting assembly also includes a king pin seated in the clevis member and located on the center line of the rear wheel. A bell crank is pivotably connected to the swing arm and supported in the clevis on the king pin, and the bell crank couples the swing arm to the clevis. The bell crank is also pivotally connected to one end of the dampening mechanism, and the other end of the dampening mechanism is connected to a strut on the swing arm adjacent its front end.
In a preferred embodiment, the dampening mechanism is a hydraulic steering piston/cylinder coupled to the steering mechanism for the front wheel to effect limited rotation of the bell crank and thereby the rear wheel assembly about the second vertical axis.